Pectins as foam stabilizers for beverages having a foam head

ABSTRACT

The invention provides pectins as new foam stabilizers for (temporary) foam heads in beverages, in particular in beers, especially beers of the pilsner type. These foam stabilizers are preferably obtained from hops, which is a constituent that is inherent in beer and accordingly offers the advantage, among others, that the foam stabilizers need to have no negative effect on the taste of the beer. Preferably, the pectins are obtained from hop cones or bines. It may be advantageous to partially saponify (de-esterify) the pectins, in connection with the number of charged groups on the pectins. In addition, the invention provides methods for obtaining the pectins and beverages stabilized with the pectins according to the invention.

FIELD OF THE INVENTION

The invention relates to the use of pectins in the stabilization of foamheads of beverages such as beer.

In addition, the invention relates to methods for producing such pectinsand beverages stabilized with such pectins.

DESCRIPTION OF RELATED ART

Pectins are polysaccharides occurring in particular in the cell walls ofdicotylous plants. The main chain of pectins contains α-D-galacturonicacid, while residues may contain L-rhamnose, D-galactose, L-arabinose,D-xylose and L-fucose. Each type of plant, in principle even eachvariety, possesses type-specific pectins whose compositions differ fromthose of the pectins of other types/varieties.

Hitherto, pectins have been used in particular in jelly-like productssuch as confiture and other fruit-jelly products. The pectins usedherein are generally isolated from apple pulp and citrus pulp (see forinstance U.S. Pat. No. 4,943,443).

U.S. Pat. No. 5,008,254 describes pectins that are isolated from sugarbeet pulp and can be used for improving various properties such asnutritional value and in many applications such as the improvement ofconsistency, non-hygroscopic adhesive, stabilizer of emulsions, etc.

In column 15 of the patent specification in question, the use of thesepectins as a foam improver is mentioned, with the understanding thatmarshmallows and imitation whipped cream are involved here.

Of course, these permanent foams cannot be compared with the foam headof a beverage such as beer.

Beer differs from other beverages through, among other things, apersistent foam head.

Owing to the natural ingredients of beer and the specific know-how ofthe brewer, a foam of good quality can be obtained.

The most important properties of such a foam are:

-   -   compactness    -   slow, regular settlement    -   good adhesion to the wall of the glass    -   formation of fine-meshed “clings” during the drying of the foam.

These parameters, which are of particular importance for the consumer'sappreciation of the beer, can be determined relatively objectively bymeans of equipment that is available on the market.

To obtain a high-quality foam, a foam stabilizer is added to variousbeers.

In general, the substance montol is used, although cobalt salts and ironsalts are used as well.

In a number of countries, the addition of such substances is notallowed, as they are not necessary for the preparation of beer and/orare not inherent to beer.

Montol is a polypropylene glycol alginate (a composition ofβ-D-mannuronic acid and α-L-guluronic acid having a molecular weight ofbetween 30,000 and 200,000). This substance is isolated from algae. Itis isolated in particular from the brown algae Laminaria digitata andMacrocystis pyrifera.

A known drawback of the use of montol, apart from the fact that it isnot inherent in beer, are the chances of precipitate formation in thefinal product.

SUMMARY OF THE INVENTION

The invention provides a method for improving the stability of the foamhead of beverages, wherein one or more pectins are added to the beveragebefore, during or after the process of its preparation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 7-1 and 7-2 each show a representation of a chromatogram.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferably added are pectins that have been isolated or extracted fromthe hop plant or other necessary starting materials for beer, on accountof the fact that these pectins are derived from an ingredient that isinherent in beer and hence Will not affect the taste properties, whichcould well be the case with commercially available pectins from, forinstance, citrus fruits.

Although hops are added in the form of hop cones, pellets, hopconcentrates or isomerized hop extract during the process of brewingbeer, their Presence does not result in the presence of pectins from thehops with a foam-stabilizing action in the eventual beer, as the processconditions of the brewing process (for instance the high temperature atneutral pH during wort boiling) lead to the breakdown of the pectins,for instance due to, inter alia, the β-elimination reaction according toAlbersheim (Albersheim et al., 1960) (the breaking of glycoside bondsnext to carboxymethyl groups). Due to this breakdown, theirfoam-improving capacity is also lost.

Hence, U.S. Pat. No. 3,099,563, which relates to foam stabilizers forbeer, starting from residual products of the brewing process, cannotrelate to pectins from hops or other beer ingredients. It is not clearwhich substances are in fact prepared with the method according to thispatent specification.

According to the present invention, it is preferred to start frompectins isolated from fresh hop parts or from by-products of the hopextraction.

Preferably, the pectins according to the present invention are obtainedfrom the hop cones or the bines of the hop plant. The pectins do notneed be isolated to a high purity, although this is in fact preferred,in particular because of the possible presence of undesired substancesthat may have a negative effect on the taste, the color or the foamstability of the eventual end product, such as for instance polyphenols.

The action of the pectins according to the invention is probably basedon the same principle as the action of montol.

Pectins as well as alginates possess a charge in beer (as described byBenard et al. Ann. Fals. Exp. Chim., 1981), enabling them to start aninteraction with beer proteins. This may lead to a more stable foam.

If this charge of the pectins is indeed relevant for thefoam-stabilizing action thereof, it may be advantageous to subject theisolated pectins to a partial saponification/de-esterification reaction.The average normal degree of esterification of 70% can then be reducedto 40-50%.

In the above-referred publication by Benard et al., pectins that may bepresent are only mentioned as being interfacing during a montoldetermination, and nothing is mentioned about any function of thosepectins.

The pectins according to the invention can be added at any desiredmoment from about 10 minutes before the end of the wort boiling (this isnot critical) to the end of the preparation process. In any case, theyhave to be added late enough to prevent the above-mentioned breakdownfrom taking place to a large extent. Preferably, the pectins are addedbefore the bright beer filtration, because any precipitates that may bepresent can be removed by means of the filtration. When, during thebrewing process, a step known as posthopping (adding a hop preparationat the end of the wort boiling) is applied, the pectin preparation cansuitably be added to this hop preparation.

The amounts of pectin that have to be added in order to achieve theimproved stability can readily be determined by a skilled person. Theywill depend on, inter alia, the purity of the pectin preparation and thetype of beer to which the preparation is added. In general, the amountof preparation to be added will be between 0.5 and 20 g/hl, preferablyaround 3 g/hl.

In principle, the invention is applicable to all types of beer for whicha foam head is desired. The invention is in particular suitable for usein for instance beer of the pilsner type. (A bottom-fermentedgold-colored beer having a characteristic hopped taste.)

According to the invention, with the pectins isolated from hops a foamstability is obtained that is at least as good as the foam stabilityobtained with montol, without the drawbacks attached thereto, and whenthe purity of the pectins is sufficiently high, even a surprisinglybetter foam stability is obtained.

The invention will be explained in and by the following examples.

EXAMPLE 1

Introduction

The stabilization of the foam with pectin is probably based on the factthat pectin has a charge in beer. As a consequence, it may formcompounds in the surface of the foam films. Hops contain 1-3% (d.s.)pectin. Hence, the pectins were isolated from hops and compared withcommercially available pectins from Quest International.

Results

When pectins are added to beer, an improvement of the foam stability canindeed be observed after incubation for 2 days by shaking of the bottle.The foam figures are given in Table 1 (Nibem meter).

TABLE 1 foam test stability minus (sec) average contr. Hop pectin (1g/hl) 276 273 274 29 5 ″ 266 285 275 40 10 ″ 282 269 275 40 Pectin 1 ″283 262 272 37 (vis 200 ) 5 ″ 283 305 289 54 10 ″ 300 301 300 65 Pectin1 ″ 275 271 273 38 (200816) 5 ″ 289 288 288 53 10 ″ 298 304 300 65Control 0 ″ 225 245 235 —

-   1. Pectin exhibits good foam stabilizing properties in dosages of 5    g/hl in beer.-   2. The foam-stabilizing properties of hop constituents are based not    only on those of the bittering substances, but also on those of the    pectins from hops.    Method

From a water extract of hop cones, pectins (1-3% d.s.) can be extractedaccording to the following method:

-   1. Incubate the extract with 0.3 N HCl at 70°for 4 hours. Then    centrifuge after the pH has been adjusted to 3 with Na₂CO₃.-   2. Next, add Al₂(SO₄)₃ and adjust the pH to 4 with Na₂CO₃. Separate    the precipitate by centrifugation.-   3. Next, add Al₂(SO₄)₃ and adjust the pH to 4 with Na₂CO₃. Separate    the precipitate by centrifugation.

The pectins were added to bottles of beer in dosages as indicated inTable 1. After this, the bottles were shaken slowly at room temperaturefor two days. Finally, at the service laboratory, the foam stabilitieswere determined in duplicate.

EXAMPLE 2

2.1 Material

Exploratory experiments were conducted with Northern Brewer A, B and C(Dutch hops). The experiments were repeated with four other varieties(German hops). Northern brewer A and B originate from the same location,Northern brewer C comes from another location.

TABLE 2 Variety of hop Hop cones Bines Waste Northern brewer A x x —Northern brewer B x x — Northern brewer C x x — Hersbrücker x x x Aromaperle x x x Northern brewer x — x Brewers gold x x x

For comparison, the foam stabilization experiments were also conductedwith commercial citrus pectin (DE 67%) and montol. For the foamexperiments, reference pilsner beer was used.

2.2 Methods

1) Pectin Extraction

The separate parts of the hop plant (bines, cones, leaves and the waste)were extracted with water (acidified to pH 2) to isolate pectin. Theprocedure followed is set forth in annex 1.

2) Determination of the AUA Content and Degree of Esterification

The purity of the isolated pectin fractions was determined by means of atitration/saponification/titration. JECFA: Compendium of food additivespecifications, volume 2, Food and Agriculture Organization of theUnited Nations, Rome 1992, p 1055.

The content of AUA (anhydrogalacuronic acid) can thus be determined.Thus, the degree of esterification (DE) of the fractions was determinedas well.

3) Determination of the Foam Influence of Pectin

The purified pectin fractions were added to beer to determine theinfluence thereof on the foam stability. The procedure is described inannex 2.

2.3 Results

2.3.1 Dutch Hops

The Dutch hop plants were harvested at two points of time to investigatevariation in the maturity of the plant (time 1 is the proper moment ofharvesting; the hop cones have the required maturity (plant A); time 2is approx. 3 weeks after the proper time of harvesting (the leaves,cones and bines are withered (plants B and C)). Table 3 shows the yieldsof the extracted pectin fractions. The leaves of all plants gave too lowa yield of pectin, as a consequence of which they are not furtherconsidered separately.

TABLE 3 Yields of extraction from the Dutch hop plants volume pectinweighed-in extraction weight % Pectin (g) (ml) (mg) extracted Bine A 20100 440 2.2 Bine B 90 500 310 0.34 Bine C 610 2600 3500 0.57 Cones A 30250 440 1.2 Cones B 75 600 520 0.69 Cones C 160 1300 1400 0.88

At the proper time of harvesting, more pectin can be isolated from thebines and cones than approx. 3 weeks after this time. Particularly thebines are sensitive to the time of harvesting (the extracted pectincontent decreases by 75-85%). The purity of the fractions also decreases(% AUA from 80 to 70). The degree of esterification of the cones andbines remains equal in time and is 75% for both.

FIG. 1 shows the influence of the hop pectins on the foam stability ofbeer in comparison with commercial citrus pectin (DE 67%) and montol (inannex 3 the results are given in tables). For dosing the pectinfractions 100% purity was assumed. However, the AUA content of bine Aand cone A is 80%, the AUA content of bines B and C and cones B and C is70%. For the comparison with montol, this should be taken into account.This was not corrected for in the experiments with the Dutch hops, butit was corrected for in the experiments with the German hops.

Up to a content of 5 g/hl, the foam-stabilizing action of bine/conepectin (A and B) is equal to the action of montol. At higherconcentrations, the action of pectin lags behind when compared withmontol (partly due to the 70-80% purity of the fractions). Bine/conepectin extracted from plant C shows a different pattern. The cone pectinhas a negative effect on the foam stability, while the bine pectin has agreater positive effect on the foam stability in comparison with binepectin of plant A and B. It is possible that in the case or the conepectin (plant C) more foam-negative components (such as polyphenols)have been extracted along.

2.3.2 German Hops

From the bines, cones and the waste of four German hop varieties, pectinwas extracted as well.

The yields are given in Table 4. In the experiments, the leaves are notconsidered on account of the low pectin yields in Dutch hop plants.

Waste is a mixture of bines, leaves and cones such as it is left in thefield after harvesting.

TABLE 4 Yields of the pectin extraction from the German hop plantsvolume pectin weighed-in extraction weight % Pectin (g) (ml) (mg)extracted Bine 1 250 1250 2.64 1.06 Bine 2 250 1250 5.46 2.18 Bine 4 2501250 4.99 2.00 Cones 1 165 1750 4.36 2.64 Cones 2 165 1750 3.26 1.98Cones 3 165 1750 2.36 1.43 Cones 4 150 1750 3.01 2.00 Waste 1 250 17504.04 1.62 Waste 2 250 1750 3.75 1.50 Waste 3 250 1750 6.73 2.69 Waste 4250 1750 4.78 1.91

From the German hops a greater pectin fraction is extracted than fromthe Dutch hops. However, the purity of these preparations is lower thanfor the Dutch hops. This is probably due to the fact that for the Germanhops more material was purified at the same time. The AUA contents areshown in FIG. 2 (in annex 6 the results are shown in tables).

The average purity of the fractions is around 60%. The degree ofesterification of all isolated pectin fractions is around 70% (in annex6 the results are shown in tables).

FIGS. 3-5 show the influence of the different hop pectin fractions onthe foam stability of reference beer in comparison with commercialcitrus pectin (DE 67%) and montol (in annex 4 the results are shown intables). In these Figures, a purity of 60% for the pectin fractions wasassumed. The concentration of the montol added was therefore alsoreduced to 60% to enable a good comparison between the two.

Bine pectin, hop cone pectin and montol give an almost equal foamstability after being added to reference beer. At an addition of 3 g/hlthe foam improvement is approx. 40 sec. At a dosage of 3 g/hl, wastepectin gives an average foam improvement of 35 sec. To all pectinfractions it applies that the stabilization is variety-dependent. If thedosage of the pectin fractions is adjusted, so that 1, 5 and 10 g AUA/hlis dosed, the foam stability is not proportionally increased (see FIG.6, in annex 5 the results are shown in tables). The fractions are only60% pure on average, the other 40% may also consist of foam-negativecomponents. If the dosage of the pectin fractions is increased, morefoam-negative components may end up in the beer as well. In order toreduce or eliminate this problem, the fractions must be purified more.

After the addition to water and beer it was investigated whether theisolated pectin fractions were detectable by means of the montol test.As a standard, mannuronic acid was included. FIG. 7 shows thechromatograms. This proves that according to this method, pectin is notdetectable. The course of the standard beer is identical to that ofstandard beer to which hop pectin has been added.

2.4 Conclusions

Pectins can be extracted from the different parts of the hop plant(bines, cones). The pectin yield from leaves was too small forexperiments. Sufficient pectin can, however, be extracted from the wastethat is left behind in the field after harvesting. The purity (AUAcontent) of the pectin fractions proves to depend on the time ofharvesting, the amount of material during purification and the hopvariety. The average degree of esterification of the Dutch hop plants is75% and of the German hop p ants 70%. Little difference is discerniblebetween bines, cones or the waste. After addition to pilsner referencebeer, “bine” and “hop cone” pectin yield the best foam improvements andthese results are comparable with montol additions. An addition of 3 gpectin or montol per hl yields a foam improvement of approx. 40 sec.

Annex to Example 2

Annex 1 Pectin Extraction from Hops

-   1 Grinding the separate hop parts (cones, leaves, bines and the    waste) (priorly freezing with nitrogen).-   2 Adding warm water acidifying with HCl of pH 2.-   3 Maintaining for 2 hours at 80° C. under constant agitation.-   4 Filtering over cheese cloth.-   5 Mixing the supernatant with alcohol 96% (1:2) without    neutralizing.-   6 Filtering over cheese cloth.-   7 Washing out precipitate 2x with 60% alcohol. Washing out    precipitate 1x with 96% alcohol (with intermediate fine-grinding    with the ultraturrax).-   8 Filtering over cheese cloth.-   9 Drying overnight in Petri dish.    Annex 2 Determination of The Foam Influence of Pectins-   1 Dried pectins were crushed and dissolved in 5 ml water under    heating before being added to beer in the following concentrations:    3 mg/bottle (approx. 1 g/hl) 15 mg/bottle (approx. 5 g/hl). 30    mg/bottle (approx. 10 g/hl). For this purpose, the pectin fractions    were assumed to be 100% pure. An experiment was conducted wherein    the addition was based on the actual purity of the pectin fractions.-   2 The bottles were shaken (50 rpm) for 48 hours (Dutch hops) or 60    hours (German hops).-   3 Measurement of the foam stability with the Nibem meter.

ANNEX 3 RESULTS OF FOAM STABILITY AFTER ADDITION OF PECTINS TO BEER(PECTINS ISOLATED FROM DUTCH HOPS) - addition based on 100% purityContent Actual Foam Test minus added content AUA stability control(g/hl) (g/hl) (sec) (sec) commercial 1 1 273 16 pectin 29-9-93 5 5 27619 control 257 sec 10 10 287 30 12-10-93 1 1 273 7 control 267 sec 5 5285 18 10 10 296 29 28-10-93 1 1 296 8 control 276 sec 5 5 313 37 10 10320 44 bine A 1 0.8 265 8 29-9-93 5 4 281 24 control 257 sec 10 8 285 2828-10-93 1 0.8 275 −1 control 276 sec 5 4 308 32 10 8 316 40 bine B 10.7 298 22 26-10-93 5 3.5 310 34 10 7 320 44 bine C 1 0.7 276 9 12-10-935 3.5 305 38 control 267 sec 10 7 318 51 28-10-93 1 0.7 283 7 control276 sec 5 3.5 328 52 10 7 — — cones A 1 0.8 265 8 29-9-93 5 4 284 27control 257 sec 10 8 284 27 28-10-93 1 0.8 265 −9 control 276 sec 5 4312 36 10 8 319 43 cones B 1 0.7 289 13 28-10-93 5 3.5 290 14 10 7 29317 cones C 1 0.7 238 −29 12-10-93 5 3.5 192 −75 control 267 sec 10 7 180−87 28-10-93 1 0.7 247 −19 control 276 sec 5 3.5 215 −61 10 7 192 −84montol 1 1 297 21 28-10-93 5 5 314 38 control 276 sec 10 10 340 64

ANNEX 4 RESULTS OF FOAM STABILITY AFTER ADDITION OF PECTINS TO BEER(PECTINS ISOLATED FROM GERMAN HOPS) - addition based on 100% purityContent Actual Foam Test minus Experiment added content AUA stabilitycontrol 15-11-1993 (g/hl) (g/hl) (sec) (sec) control water — — 302 —control water — — 306 — commercial 1 1 323 19 pectin 5 5 337 33 10 10356 52 montol 0.6 0.6 314 10 1 1 335 31 3 3 346 42 5 5 367 63 6 6 368 6410 10 381 77 bine 1 1 0.66 319 15 5 3.3 346 42 10 6.6 354 50 bine 2 10.75 323 19 5 3.75 343 39 10 7.5 374 69 bine 4 1 0.64 320 16 5 3.2 33632 10 6.4 468 64 cones 1 1 0.61 325 21 5 3.05 351 47 10 6.1 365 61 cones2 1 0.65 316 12 5 3.25 342 38 10 6.5 366 62 cones 3 1 0.56 319 15 5 2.8346 42 10 5.6 360 56 cones 4 1 0.6 313 9 5 3 341 37 10 6 359 55 waste 11 0.55 320 16 5 2.75 — — 10 5.5 345 41 waste 2 1 0.56 320 16 5 2.8 33935 10 5.6 351 47 waste 3 1 0.72 309 5 5 3.8 334 30 10 7.2 360 56 waste 41 0.65 314 10 5 3.25 343 39 10 6.5 352 46

ANNEX 5 RESULTS OF FOAM STABILITY AFTER ADDITION OF PECTINS TO BEER(PECTINS ISOLATED FROM GERMAN HOPS) - addition based on purity measuredContent Actual Foam Test minus Experiment added content AUA stabilitycontrol 19-11-1993 (g/hl) (g/hl) (sec) (sec) control water 301 — bine 15.2 1 322 21 31 5 348 47 51 10 359 58 bine 4 4.7 1 323 22 23 5 341 40 4710 373 72 montol 1.8 1.8 311 10 3 3 329 28 9 9 343 42 15 15 358 57 18 18369 68 30 30 378 77

ANNEX 6 PURITY OF THE PECTIN FRACTIONS (AUA CONTENT) AND DEGREE OFESTERIFICATION (DE) OF THE GERMAN HOP VARIETIES Sample AUA (mg) AUA (%)DE (%) pectin 285 95 69 commercial bine 1 146 66 76 bine 2 227 75 70bine 4 192 64 73 cone 1 183 61 69 cone 2 194 65 75 cone 3 164 56 72 cone4 181 60 68 waste 1 164 55 75 waste 2 167 56 77 waste 3 225 72 70 waste4 195 55 77

EXAMPLE 3

3.1 Material

Residues of the following hop extracts were used:

-   A Ethanol extract residues-   B CO₂ extract residues-   C CO₂ extract residues-   D Hexane extract residues.

For comparison, the foam-stabilization experiments were also conductedwith commercial citrus pectin (DE 67%), montol and priorly purifiedpectin fractions from hop bines and hop cones (Example 2).

For the foam experiments reference beer was used.

3.2 Methods

3.2.1) Pectin Extraction

The ground residues were extracted with water (acidified to pH 2) toisolate pectin. The procedure followed is set forth in annex 1.

3.2.2) Determination of the Foam Influence of Pectin

The purified pectin fractions were added to beer in order to determinethe influence thereof on the foam stability. The procedure is describedin annex 2.

3.3 Results

From different hop suppliers residues were obtained that are left behindafter the production of hop extracts. From these residues pectins wereisolated. The yields are shown in Table 5. The yields of pectin fromthese residues are comparable with the yields from fresh material (conesand bines). Residues from CO₂ extracts were obtained from two suppliersand reveal different pectin yields. However, the extraction procedurefor the two suppliers is not completely known and different hopvarieties were used. Example 2 has shown that the variety influence theamount of pectin that can be isolated.

TABLE 5 Yield of pectin fractions purified from residues formed duringthe preparation of different hop extracts Sample Pectin yield (%)residues ethanol extract A 2.3 residues CO₂ extract B 1.8 residues CO₂extract C 2.5 residues hexane extract D 2.4

FIG. 8 shows the influence of the residual pectins on the foam stabilityof pilsner beer in comparison with commercial citrus pectin, montol andbine pectin (see Example 2). In annex 3 the results are given in tables.For dosing the pectin fractions 100% purity was assumed. However, theAUA content of the residual fractions will be lower (was notdetermined). For the comparison with montol, this should be taken intoaccount.

The foam-stabilizing action of pectin from ethanol and hexane extractresidues is not substantial. Beer to which these pectins were addedexhibits a foam stabilization that is virtually equal to that of controlbeer. A positive effect can be observed after the addition of pectinsfrom residues of CO₂ extracts. At an addition of 10 g pectin/hl, thefoam improvement is 26 sec. The pectins from bine and cones (previousexperiment) give an increase of 40 sec, however without correctionshaving been made for the purity of the fractions.

Annex 1 (to Example 3) Pectin Extraction from Hops

-   1 Grinding the different extracts (priorly freezing with nitrogen).-   2 Adding warm water (water material ratio, see Table 4.1),    acidifying with HCl to pH 2.-   3 Maintaining for 2 hours at 80° under constant agitation. Filtering    over cheese cloth. Mixing the supernatant with alcohol 96% (1:1.5)    without neutralizing.-   4 Filtering over cheese cloth.-   5 Washing out precipitate 3x with 96% alcohol.-   6 Filtering over cheese cloth.-   7 Drying overnight in Petri dish.    Annex 2 (to Example 3) Determination of the Foam Influence of    Pectins-   1 dried pectins were crushed and dissolved in 5 ml water under    heating before being added to beer in the following concentrations:    15 mg/bottle (approx. 5 g/hl) and 30 mg/bottle (approx. 10 g/hl).    For this purpose, the pectin fractions were assumed to be 100% pure.-   2 The bottles were shaken (50 rpm) at room temperature for 60 hours.-   3 Measurement of the foam stability with the Nibem meter.

ANNEX 3 FOAM STABILITY OF BEERS TO WHICH DIFFERENT PECTIN FRACTIONS WEREADDED (to Example 3) Amount Foam Increased added stability stabilitySample g/hl sec sec Control — 280 — Control water — 300 — Residueshexane — 300 0 extract A 10 294 0 Residues CO₂ 5 302 2 extract B 10 32727 Residues CO₂ 5 300 0 extract C 10 326 26 Residues ethanol 5 296 0extract D 10 298 0 Montol 5 345 45 10 361 61 Commercial 5 323 23 pectin10 355 55 Bine 1 10 344 44 Cones 1 10 338 38

1. A method for improving foam head stability in beer, comprising addinga hop extract containing at least 20% anhydrogalacturonic acid on a dryweight basis of extracted material, to a beer preparation aftercommencement of wort boiling and not earlier than 30 minutes before theend of wort boiling, said hop extract being added in an amount of atleast 0.5 g per hectoliter of said beer preparation.
 2. The methodaccording to claim 1, wherein said hop extract is added not earlier than10 minutes before the end of wort boiling.
 3. The method according toclaim 1, wherein said hop extract is added subsequent to wort boilingbut prior to bright beer filtration.
 4. The method according to claim 1,wherein said hop extract is added in an amount from 0.5 to 30 g perhectoliter.
 5. The method according to claim 1, wherein said hop extractis made by extracting a by-product of a hop extraction process or byextracting hop bines.
 6. The method according to claim 5, wherein saidby-product is an extraction residue obtained from CO₂ extraction.